(6) 6AK5 Low Noise Pentode Tubes by SARKES TARZIAN (JCBGB-6AK5W)
They are low-noise, miniature 7-pin tubes. They have black plates and top square getters. Test readings are as follows: 88, 88, 86, 82, 82 and 90. The good range is from 50 to 100 on the scale. Production codes are as follows: 215, 215, 226, 239, 239 and 239.